Planetary Carbon Sequestration: Earth's Biosphere Flexes Its Muscles
Ten years ago, many people were fearful the air's CO2 content would rise in direct proportion to the magnitude of humanity's ever-increasing emissions of carbon dioxide. Idso (1991a,b), however, felt otherwise. He predicted the air's CO2 content would rise at a rate that would be a declining percentage of anthropogenic CO2 emissions, because he felt the productivity of earth's plant life would rise in response to the ongoing increase in the air's CO2 content - due to the well known aerial fertilization effect of carbon dioxide - thereby resulting in ever more CO2 being removed from the atmosphere each year. Today, he appears to be vindicated by real-world data, as Wofsy (2001) reports in a Climate Change article in Science magazine that "emission rates of CO2 from combustion of fossil fuel have increased almost 40 percent in the past 20 years, but the amount of CO2 accumulating in the atmosphere has stayed the same or even declined slightly."

What is responsible for this largely unanticipated turn of events? In a word, the biosphere. Much like Rodney Dangerfield, "it don't get no respect." For years environmentalists have warned us about how fragile earth's biosphere is; and in many cases dealing with specific species or ecosystems, they have been correct. In its totality, however, the biosphere is much more resilient than most people give it credit for being. As atmospheric CO2 - the lifeblood of the planet - has gradually risen over the course of the Industrial Revolution, for example, the biosphere has begun to reveal its true strength, with the plants of the planet growing ever more robustly and profusely, as they expand their ranges over the face of the earth and extract ever greater quantities of CO2 from the air and sequester its carbon in their tissues and the soil into which they sink their roots (Idso, 1995).

A good case in point is the vegetation of the coterminous United States. Pacala et al. (2001) report in a recent article in Science that estimates of the country's 48-state carbon sequestering power have grown significantly over the past several years, from a range of 0.08-0.35 x 1015 grams of carbon per year (Pg C yr-1) in the 1980s to a range of 0.37-0.71 Pg C yr-1 today, with some evidence suggesting values as high as 0.81-0.84 Pg C yr-1 (Fan et al., 1998). Likewise, we read in another report in the same issue of Science that carbon sequestration in China is growing like gangbusters as well (Fang et al., 2001). With a little help from the government via several "ecological restoration projects" aimed primarily at afforestation and reforestation, the world's most populous country has turned around what had been a losing proposition with respect to carbon capture by forests to where it has now been increasing its forest carbon sequestration rate by an average of 0.021 Pg C yr-1 for about the last two decades.

Yes, we are by no means headed for a runaway atmospheric CO2 greenhouse effect, or even a runaway atmospheric CO2concentration. The biosphere - helped by man's overt husbandry of its plant life (forests, in particular) and his inadvertent fertilization of the air with the carbon dioxide he produces - is beginning to exert a powerful brake on the rate of rise of the air's CO2 content, such that the large increases in anthropogenic CO2 emissions of the past two decades have not resulted in any increase in the rate of CO2 accumulation in the atmosphere. Hence, there is every reason to believe that by the judicious application of management techniques designed to foster carbon sequestration in earth's terrestrial ecosystems, the atmosphere's CO2 concentration may actually be stabilized in the not too distant future, as more plants growing more robustly - thanks to the aerial fertilization effect of atmospheric CO2 enrichment - flex their muscles and constrain the air's CO2 content to a new equilibrium level that forestalls any threat of CO2-induced global warming while concurrently stimulating earth's plant life to achieve the higher productivity level that will be required to feed the planet's burgeoning population that is expected to level out at approximately the same time the air's CO2 concentration does (Idso and Idso, 2000).

Sounds a lot like a win-win situation for man and nature alike ... and without the onerous burden of superfluous regulations and taxes. The biosphere can clearly have its carbon dioxide cake, and eat it too!